%ErFen二分法
clear
clc
eps=5e-6;
delta=1e-6;
a=1;
b=2;
fa=f2_1(a);
fb=f2_1(b);
n=1;
while(1)
    if(fa*fb>0)
        break;
    end
    c=(a+b)/2;
    fc=f2_1(c);
    if(abs(fc)<delta)
        break;
    elseif(fa*fc<0)
        b=c;
        fb=fc;
    else
        a=c;
        fa=fc;
    end
    if(b-a<eps)
        break;
    end
    n=n+1;
end
n
c
fc